Spark plug



Aug. 31, 1948. D. E. REPLoGLE snnx gwn Filed Jan. 25. 1944IIIIIIIIIII4IIJ f fin/474124,

INVENTOR.

Patented Aug. 31, 1948 UNITED STAT-ES PATENT GFFICE SPARK PLUG DelbertE. Replogie, Ridgewood, N. J., assignmto Global Spark Plug Co.,Paterson, N. J., a corporation of New Jersey Application January 25,1944, Serial No. 519,670

struction of the spark plug and a step in the method of formation;

Fig. 2 is a similar view illustrating a subsequent' step in the processof formation of this spark plug;

Figs. 3 and 4 are 'sectional views of a modied method of manufacture ofa spark plug; and

Fig. 5 is a vertical sectional view of a special formation of thecentral part of the shell of the spark plug.

The spark plug of this invention comprises an outer shell IIJ preferablyof cold rolled steel, an insulator II at the lower portion of the shell,a molded insulation I2 filling the shell above the insulator II, and a.central electrode I4 preferably of molybdenum with an end or sparkingpoint I5 of nickel or similar resistant metal.

The shell I has a tapered seat I6 for the insulator II, a bushing I1intervening between the insulator and the seat and being composed ofcopper or other soft metal providing an intimate sealing contact withthe cooperating surfaces of the seat and insulator.

The insulation I2 is molded in place under heat and pressure in a mannergiving a thorough leakproof seal While at the same time rigidly fixingall of the parts in place and insulating the rod or electrode I4 fromthe Ashell I0.

On the outside the shell I0 is provided with flange I 3, nut portion i9and threads 2li for the fastening of the spark plug in place in theengine.

The sparking end of the plug is provided with a recess 22 around thelower end 23 of the insulator II and a plurality of sparking points 24are arranged around the end I of the central sparking electrode.

The top of the shell I0 is provided with an overhangin-g flange ringforming a ledge around the recess 3| for the reception of the terminalconnection, the inner end of which reaches and contacts with the head 32at the top of the central electrode I4 at the bottom of 1 Claim. (Cl.12S-169) the recess 3|. Screw threads 33 are cut around the outer end ofthe shell above the shoulder 34 to cooperate with the outer attachingsleeve of the standard terminal fitting in recess 3| and held therein bythe screwing of the sleeve on to the threads 33.

As shown in Fig. 5 the head 320 on the electrode |40 may be speciallyshaped m'th a neck portion 35 between the ends 36, 31, the upper surfaceof the latter forming the bottom of the recess 3|0. The shell IllII mayhave its central portion 38 bulged outward in globular formation asshown to give additional thickness of insulation between the head andthe -shell and to aid in anchoring the molded insulation |28 securely inplace.

In the formation of the spark plug the shell III is assembled with theliner or bushing I1 in place on the seat I6 and insulator I I pressedinto place. The rod I4 is then inserted with its lower end part way inthe bore of the insulator (Figs. 1 and 3). The insulation I2 for moldingis then supplied, preferably in powdered or granular form, substantiallyfilling the shell I0 above the insulator II, and a plunger 40 having asliding fit in the flange ring 30 is forced downward into the shell tocompress the insulation, the whole plug with the insulation being heatedto a high temperature to render the insulation I2 plastic and moldable.A's the plunger 40 descends, the pressure increases and the rod I4 movesdownward with the plunger, the now plastic insulation flowing into allcracks and crevices of the shell and insulator parts and upward aroundthe plunger 40 and under the flange ring 30 as indicated in Fig. 2.During this plunger action the lower end I5 of the rod I4 protrudesoutward below the lower end of the spark plug an amount dependent uponthe length of movement of the plunger 40, and at the end of the plungermovement the molded insulation I2 has completely and tightly filled theentire space within the shell and has formed a permanent leakage-proofseal. The plunger 40 is then removed leavin-g the recess 3| with thecontact head 32 at the bottom and the lower end I5 of the centralelectrode I4 is cut off about even with the sparking points 24 as shownfor instance in Fig. 5.

The cooling of the molded insulation I2 hardens the insulation intosolid glassy formation, all of the parts being tightly bound together.Preferably, the outer shell I0 is of material, such as cold. rolledsteel, having a. relatively high coemcient of shrinkage on cooling incomparison to aus, los

the material molybdenum, for instance, of the central rod M, theshrinkage of the molded mass i2 being intermediate between these so thatthe sleeve of molded material l2 tightly grips the rod M and in turn istightly gripped by the shrinking of the shell i0.

As illustrated in Figs. 3 and (i, the molded plunger 50 may b of hollowformation with o, bore Iii sliding over the rod 0i! forming the centralelectrode and the periphery of the plunger 50 having a sliding it withinthe flange ring lit. The further depression of the plunger E0, forinstance to the extent shown in Fig. 4, Will cause the heated insulatingmaterial i?. to ovv into all parts of the interior of the shell, and atthe se time the electrode 03 will move downward with said material, inthis case being received in the template @5, limiting its downwardmovement and positioning it relative to the sparking points 20. Theplunger 00 isthen removed and the recess 0o is formed similar to therecess 0i to receive the conventional terminal connection.

The molded insulation i?. is preferably of the glass bonded mica type asset forth for instance in U. S. Patent 1,795,200 and Re. Patent 15,727to Crossley or U. S. Patent 2,032,239 to Wedloclr, as

this will give a rrn bonding and sealing e`ect while at the same timeproviding a, superior type of insulation.

The completed sparlr plug is strong and durable, effectively insulatingthe central electrode l0 and also absolutely tight against the leakageof pressure through the plug so es to be permanently leakproof.

I claim: v

A shielded spark plug comprising a tubular ,rn/etal shell having one endportion provided with a seat for an insulator and the other end portionof cylindrical form with'an intermediate centralportion bulged outwardto larger diameter in globular formation. a tubular insulator on saidseat, an electrode passing through said insulator and connected at itsinner end to a head member extending into said globular formation andhaving an intermediate narrow neck portion, and a molded insulationfilling said globular formation and said shell behind said insulator andaround said neck portion oi said head to retain said insulator againstits seat and lock said head in place in said globular formatlonandretain the parts against relative axial movement in either direction.

DELBERT E. REPLOGLE.

REFERENCES (CNED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 960,784v Anderson Aug 0, 19101,361,562 Schmidt `met. 2, 101? 1,300,232 Landa May i0, 1020 1,035,100Littleton July 12, 1027 1,848,312 Bruzzone Mar. 8, 1932 1,369,133 Beverset al July 26, 1932 1,074,208 Case Sept.' 10, 1934 2,240,415SchWartZWnlder et nl.-- July 1941 2,250,810 `Rabezzena et al Oct. 14,1041 FQREIGN PA Number Country Date 3,085 Great Britain Feb. 21, 1000106,037 Australia Mar. 16, 1030 230,037 Great Britain Aug. 2'?, 1025France Apr. 27, 1022

